Oxygraphic evaluation of mitochondrial function in digitonin-permeabilized mononuclear cells and cultured skin fibroblasts of patients with chronic progressive external ophthalmoplegia.

For quantitative elucidation of maximal mitochondrial oxidation capacities in human mononuclear cells, cultured human skin fibroblasts and human thrombocytes the optimal amount of digitonin for plasma membrane permeabilization was determined to be 5, 10, and 0.1 micrograms/10(6) cells, respectively. Using these concentrations the rate of respiration of permeabilized cells with the mitochondrial substrates succinate (+ rotenone) or glutamate + malate can be stimulated between two- and fourfold by ADP and inhibited by carboxyatractyloside. The maximal respiratory activities of well-characterized preparations of permeabilized mononuclear cells of five patients with chronic progressive external ophthalmoplegia were compared to healthy controls and a 30 to 50% decrease of the ADP-stimulated respiration rates with glutamate + malate and succinate + rotenone was detected. This is an indication for the presence of the mitochondrial defect in respiratory active blood cells. Additionally, for two of these patients the mitochondrial defects were proven to be detectable by the determination of maximal oxygen consumption rates of digitonin-permeabilized cultured skin fibroblasts. Therefore, the determination of maximal oxidation capacities of a well-defined cell population using strictly standardized conditions of digitonin permeabilization is judged as a useful and sensitive method for the elucidation of mitochondrial function in extramuscular tissue.